In the past, various and sundry different types of thermostats have been employed for effecting regulation of the temperature of a space in which the thermostat may be located, and various different types of means have been employed in such thermostats for sensing the temperature of the space. For instance in some of the past thermostats which employed a temperature sensing means comprising a bimetal element having a generally spiral configuration, such spiral bimetal element had a pair of inner and outer generally radially spaced ends, and the inner end was attached by suitable means to a post rotatably mounted on a base plate of the thermostat casing. The spiral bimetal element and the post were conjointly rotatable in response to the manual adjustment of a temperature selector to a set-point temperature desired for the space in which the thermostat was located. Thus, the spiral bimetal element was rotated to adjusted positions correlative to the set-point temperatures indicated by the temperature selector in response to the manual movement thereof by an operator of the thermostat, and in respective ones of such adjusted positions correlative with the particular selected set-point temperature, the spiral bimetal element expanded or contracted in response to variations in the temperature with respect to such selected set-point temperature of the space in which the thermostat was located. In this manner, the temperature sensing movement, i.e. the aforementioned expansive or contractive movement of the spiral bimetal element, was translated into or was operative to effect a switching operation of the thermostat. In other words, when the thermostat was in a selected one of its heating or cooling operating modes, the temperature sensing movement of the spiral bimetal element was effective to cause a switching operation so as to initate or terminate the operation of a heating or cooling device conditioning the temperature of the space in which the thermostat was located.
Of course, this aforementioned switching operation of the thermostat in response to the temperature sensing movement of the spiral bimetal element was effected in various different manners. For instance, as illustrated in U.S. Pat. No. 3,993,120, either one or a pair of mercury switches were predeterminately positioned on a mounting bracket attached to the radially outer end of the spiral bimetal element so as to be conjointly movable with the spiral bimetal element in response to the temperature sensing movement thereof, and of course, such movement of the mercury switches affected the switching operation thereof so as to control the heating or cooling operating modes of the thermostat. In U.S. Pat. No. 3,656,082, a permanent magnet was attached to the radially outer end of the spiral bimetal element, and the temperature sensing movement of the spiral bimetal element conjointly moved the permanent magnet so as to operate a magnetically actuated reed-type switch associated therewith in order to control the heating or cooling operating modes of the thermostat.
In U.S. Pat. No. 2,539,259 a pair of pivotally movable magnets were respectively driven by the temperature sensing movements of a strip-type bimetal element so as to operate a pair of movable or magnetically actuated electrodes in a mercury switch associated therewith in order to control the heating or cooling operating modes of the thermostat.
In U.S. Pat. No. 3,573,698, one end of a generally U-shaped bimetal element was biased so that the temperature sensing movement of the other end of such bimetal element was correlative with the set-point temperature selected in order to effect the biasing of the one end of such bimetal element. The other end of the generally U-shaped bimetal element carried a pair of armatures respectively movable toward and away from magnetic coupling engagement with a permanent magnet associated therewith and encapsulated in a reed-type switch. The temperature sensing movement of the armature with the generally U-shaped bimetal element attracted the magnet within the reed-type switch between a pair of generally opposite switching positions to control the heating and cooling mode operations of the thermostat.